Fixed atomic reindex to ensure init when check_settings=true.

[metheglin]

Q	A
Bug fix?	Probably yes
New feature?	Probably no
BC breaks?	Probably no
Related Issue
Need Doc update	Probably no

What problem is this fixing?

Atomic reindex (ex: Product.reindex) is always going to create tmp index with empty setting. And index move completed, previous settings disappeared. Not only specified settings inside algoliasearch block, but manual setting on dashboard.

How to Reproduce

app/models/product.rb

class Product < ApplicationRecord
  algoliasearch check_settings: true do
    attribute :title
    attribute :content
    attribute :updated_at_i
    
    customRanking ['desc(updated_at_i)']
    searchableAttributes ['title']
    indexLanguages ['ja']
  end
end

in rails console for instance

Product.reindex
  # Check dashboard, all specified settings are disappeared.
  # Not only specified settings inside algoliasearch block, but manual setting on dashboard.

Describe your change

I understood the check_settings specification like this:

When check_settings: true (default), all the index operation going under ActiveRecord respect the specified settings in algoliasearch block.
On the other hand when check_settings: false, users just want to manage it on dashboard. So when new tmp index is to create, it just takes over the settings from existing index.

If my understanding is true, I guess current implementation accidentally missed algolia_ensure_init for tmp index when check_settings=true. I have imported that case from previous version below.

https://github.com/algolia/algoliasearch-rails/blob/9c1a0a46ca3dd4487cc3461c755a3fef144db491/lib/algoliasearch-rails.rb#L554C23-L554C86

[DevinCodes]

Hey @metheglin , thank you for your PR! Did you test out your changes by any chance to confirm the behaviour after this change is as expected? 🙂

[metheglin]

@DevinCodes

Thank you for reply.
I only confirmed that my problem resolved. With version 3.0.0, Product.reindex always rollback every settings even though settings described in ActiveRecord model (See "How to Reproduce"). With this PR version, I can check that settings described in model are well maintained on dashboard with latest data.